[services-ng] drop support of postgresql 8.x

drop support postgresql 8.x, remove the case...when to check the major version.

unit-test passed and yeti-test passed (plan 100, 200)

There are some failures in yeti-test that caused by buildpack staging and not relative to the service itself.

Change-Id: Iff0c9bff9db38f2e93f2c0df65bf87c6107e3644